new Infusoria from American Fresh Waters. 445 



located ; anal aperture subterminal. Length of body ^ to 

 Tffo inch. 



Hah. A vegetable infusion. Reproduction by transverse 

 fission. 



For some time this was the prevailing form in an infusion, 

 gliding over the fungoid slime on the surface as visible 

 whitish spots. By transmitted light it is brown and semi- 

 opaque. 



The structure of the peristome is complex, resembling that 

 of the same part in Gastrostyla Steinii, Eng. The series of 

 fine " paroral " cilia on the left-hand border of the region, in 

 addition to the large adoral cirri on the same margin, 13 

 especially notable, as it has but seldom been observed in any 

 animalcule. 



A nucleus does not seem to be invariably present. Only 

 one has been noticed in any individual, and in many instances 

 none could be perceived even after treatment by reagents and 

 staining-fluids. 



The food consists chiefly of the smaller animalcules, the 

 rhizopod Trinema enchelgs, Leidy, and in several instances of 

 small Anguillulce, all of which were observed within the endo- 

 plasm, while an unsuccessful effort to swallow a large Anguil- 

 lula was noted. 



Opisthotricha emarginata, sp. nov. (PI. XV. fig. 2.) 



Body elongate, obovate, soft and flexible, depressed, about 

 four times as long as broad, widest, anteriorly, the frontal 

 bolder rounded ; somewhat tapering to the posterior extremity, 

 the right-hand margin of which is conspicuously emarginate ; 

 peristome-field arcuate, narrow, without an inner or right- 

 hand border, extending from the frontal margin for about one 

 third the length of the body ; eight frontal styles, six scattered 

 setose ventral, and five large conspicuous anal ones ; marginal 

 setse scarcely interrupted at the posterior extremity, more 

 numerous on the right-hand border ; caudal setai three ; 

 several longitudinal rows of hispid seta3 on the dorsal surface : 

 nucleus double, ovate ; contractile vesicle single, spherical, 

 close to the left-hand border, near the posterior termination of 

 the peristome. Length ^0 to -jy-^ inch. 



Hah. Standing water, with aquatic plants. Reproduction 

 by transverse fission. 



In its movements this infusorian is rapid and erratic. Fre- 

 quently after remaining comparatively quiescent, it suddenly 

 darts backward entirely out of the field of the objective. 



The contractile vesicle expels its contents through the 

 dorsal surface, at complete systole forming there a conspicu- 

 ously projecting elevation of the cuticular surface. 



Ann. &Mag.N. Hist. Ser. 5. Vol. xv. 31 



